1. Field of the Invention
The present invention relates to a car door apparatus that is installed to a car of an elevator, and particularly, to the air ventilation structure of a car having airtightness in emergency situations.
2. Description of the Related Art
A car of an elevator moves upward and downward inside the elevator shaft of a building with passengers accommodated therein. Passengers inside the car come to feel annoyed with a change of air pressure during the upward and downward movement when the difference of running elevation goes beyond 300 meters. Furthermore, the passengers begin to be affected physiologically in auditory organs when the elevating speed becomes significantly high.
So as to suppress the affection, in an elevator, a car may be sometimes provided with an air pressure control device for controlling and adjusting air pressure inside the car. In this case, the car includes a pressurization blower that compresses air and sends thus compressed air to pressurize the inside of the car, and a exhaust blower that exhausts air to decompress the inside of the car, which function as the air pressure control device. When the pressurization blower and the exhaust blower are arbitrarily driven, air pressure inside the car is adjusted depending on the changing of external air pressure.
The car provided with such an air pressure control device is required to have a high airtightness therein. However, when the airtightness of a car is increased, there is a problem in a case the car is stopped in an emergency with passengers confined in it, causing a power source for driving the elevator to be shut off due to electric power failure, etc.
When a car is supplied with power, the pressurization blower and the exhaust blower of the air pressure control device may ventilate the car. However, if the car is stopped in an emergency when the air pressure control device cannot be driven in a case that the power source is shut off due to electric power failure, etc., the car cannot be ventilated. Accordingly, the density of oxygen in the car becomes thin, which not only makes passengers feel uncomfortable but may also result in a serious problem regarding safety when the situation continues for a long time.